This invention relates in general to gun barrels and in particular to a new and useful method of forming the gun barrel and to the gun barrel construction.
The present invention relates to a tube, particularly a gun barrel having its inside surface coated with a thin layer of a hard material, to protect the inside surface against wear and corrosion and to reduce the friction and to a method of forming the barrel.
In order to improve the adhesion and resistance to abrasion of vacuum deposited layers, various measures have already been taken. For example, it is known that layers deposited by cathode sputtering adhere to certain surfaces better than layers applied by usual vapor deposition. An increased adhesion is also obtained with the recent methods of ion-assisted vapor deposition.
However, all of these prior art methods are of no use if such layers are exposed to a stronger and more frequent tensile load, as in the case of gun barrels during a discharge, for example.
Tubes with a coated inside surface are employed for most various purposes and while using most various methods of coating, such as sealing in (German OS 28 41 295 and 32 37 655), chemical precipitation from a gaseous phase (German OS 27 18 148), vapor deposition (U.S. Pat. No. 4,354,456 and 4,407,712), or cathode sputtering (German AS's 28 20 301; 26 55 942; 27 29 286; 31 50 591; German Pat. No. 976 529).
Coating of gun barrels is mentioned expressly only occasionally such as in Gipson (German Pat. No. 31 50 591), in connection with a cathode sputtering method, or in Koniger (German Pat. No. 25 37 623) and in Meistrung (German AS 28 09 709).
It would be advantageous to provide gun barrels with an inner coating of hard materials, to improve their resistance to wear and corrosion and reduce the friction. In spite of that, no successful coating of this kind is known up to the present time. The assumed reason is that the adhesion of the layer of hard material is not sufficient. This is a problem which evidently does not occur in the actually applied diffusion hardening where the interface problem does not arise.
German AS 28 09 709 describes an about 1.3 mm thick ceramic layer which is applied in a thermal spraying method to a core and then transferred from the core by shrinking there on a tube. A layer of such thickness, of course, has a high stability of its own and therefore does not depend merely on the adhesion to the substrate, as the layers considered have a thickness less than 10 micrometers (microns).
The mentioned ceramic layer is therefore rather an inserted ceramic tube which has been produced in a spraying process.